<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html lang="en">
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>box1</title>
	<script type="text/javascript">
	window.onload = function  () {
			box = document.getElementsByClassName("box");
			x=0
			box[0].onmouseover = function run () {
				box[0].style.height = "400px";

				box[0].style.width = "400px";

				
				  }

				box[0].onmouseout = function run () {
					
				
				box[0].style.height = "200px";

				box[0].style.width = "200px";

				}



			
		  

	}





	</script>
	<style type="text/css">
			.box{
				width: 200px;
				height: 200px;
				background: #A349A4;
				border-radius: 50%;
			}
	</style>
</head>
<body>
		<div class="box"></div>
</body>
</html>